As is known, in many buildings, whether these be for industrial use, or for use in the handicrafts, commercial or residential sectors, for example factories, workshops, hospitals, hotels, tenement blocks, individual dwellings, shops, trading centres, etc., there are currently used in an increasingly extensive way more or less complex wiring systems that enable transmission of different types of signals to the various parts of the building, for example transmission and distribution of electricity, telecommunications, computer systems, various systems for protection and control, and so forth.
In such wiring systems, a basic component that is widely used in the art is represented by the so-called ducts or raceways or wireways, which are assembled one after another so as to form a sort of duct or trough that “carries” the various cables from the sources to the loads according to pre-set paths, and constitutes a compartment that houses the cables, protecting them as much as possible from the external environment.
Currently, according to the uses and the applicational needs, there are available different types of ducts, and amongst these, one of the most widely used is the wire-mesh duct.
In their most essential embodiment, these wire-mesh ducts are made up of a grid of metal wires that can be of two types, namely, a first type of wires arranged according to the longitudinal development of the duct, which constitutes the warp of the grid (“warp wires”); and a second type of wires that are arranged in a transverse direction with respect to the longitudinal wires and constitutes the weft of the grid (“weft wires”). The two types of wires are welded together and form a normally U-shaped channel or trough, which, once the cables have been housed therein, is usually closed with an appropriate cover.
Thanks to this structure, wire-mesh ducts are particularly appreciated both by manufacturers, on account of their relative simplicity and economy of production, and above all by installers. In fact, they present high effectiveness of use, for example in terms of operating flexibility, in that to make connections along the path the various cables may be made to exit from any one of the meshes of the grid, in terms of ease of inspection and identification through the meshes of the grid of the types of cables on which operations may be carried out, in terms of cleanliness of the duct itself, in terms of natural ventilation of the cables, etc.
Notwithstanding this, the intrinsic structure of the above ducts, if on the one hand it is the principal reason for their commercial success, on the other hand, it is at the same time the source of certain critical factors and some not altogether satisfactory technical aspects.
In particular, the extreme essentiality of implementation results in a normally modest structural rigidity and in practice in a reduced mechanical resistance to loading; this clearly limits the dimensions of the duct and the loads that it is able to withstand, which, if they are excessive, could lead to problems of bending or even to deformation. Consequently, either the carrying capacity of the ducts is to be limited, and hence the number of cables used, in particular when the duct is in a position suspended from resting surfaces, such as floors, or else, as is usually the case, it is necessary to resort to the use of appropriate supports or jointing devices, or again particular constructional solutions are adopted that enable improvement of their mechanical performance. In this sense, two examples of possible solutions adopted in the art are described in the patent applications US2001/0009192 and EP1195869.
The above different solutions, albeit valid, in general adversely affect, at least partially, the advantages afforded by such ducts in that the production costs increase on account of the use of additional pieces or of the adoption of particular production processes, and/or the difficulties of installation are increased. It is necessary, in fact, to consider that usually the channels are arranged in positions that are not particularly convenient to reach and in narrow spaces, and hence the use of supports or jointing devices is not always easy.
Another critical factor of wire-mesh ducts of a known type is represented by the fact that the ends of the weft wires are normally exposed and have sharp edges that during positioning may either damage the cables or cause injury to the installers. Furthermore, on account of these sharp edges, the coupling of the ducts with the cover is problematical, and the cover itself may even suffer damage. To overcome these problems different solutions are adopted; for example, the sharp edges are rounded off, or else the ends of the wires are bent back. Other approaches to the problem envisage the adoption of particular constructional solutions, as, for example, described in the European patent application EP0352191, or the coating of the ends of the wires with appropriate protective elements that then favour coupling with the cover, as is, for example, described in the patent application EP1206022. Also these solutions, albeit effective, have, however, adverse repercussions on the costs of production and of laying in place.
Finally, the process of welding between the wires itself, taking into account also the substantial number of junction points, is not altogether satisfactory since it is necessary to resort to welding methods, typically induction welding, which are in themselves critical and entail the use of complex and costly equipment